The present invention relates generally to tools used in the practice of dentistry and more particularly to the assembly of a dental tool handpiece wherein tool members are replaceably engaged during performance of dental operations.
In dental tool handpiece assemblies presently known in the art, the length of the shank or body portion of a tool, such as a drill or other device, which is normally inserted into the handpiece tends to be of a standardized size. In tools which utilize angled handpieces, the shank of a drill or similar tool member which is to be utilized with such a handpiece is usually much shorter than other shank lengths. However, there arises a need to enable tool members or drills of both types or categories to be inserted within a straight handpiece. In this connection, it is desirable also that drills with short shanks be provided with an axial abutment surface to support the drill in the same manner as would ordinarily occur with drills having longer shanks.
In order to achieve the purposes discussed above, pins have heretofore been utilized with dental tool handpieces. The pins are inserted into the bore defined by the collet of the handpiece and the length of the pin corresponds to the difference in the shank length of the tool members which are to be utilized thereby operating as spacer members to take up the gap between the shank end of the tool and the abutment surface provided within the handpiece.
However, pins of this type can be utilized satisfactorily only so long as they can be readily removed from the bore of the collet without difficulty when a tool member or drill is to be changed. Normally, it is necessary that such pins merely drop or fall out of the collet bore when the handpiece is held in a downwardly facing or oblique position. With increasing length of use of such pins within the collet, the collet tends to accumulate foreign matter or becomes disposed so that the pin will tend to stick within the collet making removal of the pin difficult or impossible. In such a case, the handpiece assembly must be disassembled and taken apart in order to enable removal of the pin. Generally, it is usually at least necessary that the collet be removed so that it may be reinserted in a manner providing an adjustment to insure the proper damping effects.
Operation of a dental handpiece without an abutment pin generally gives rise to the danger that the tool may slip into the collet and remain trapped there so that, again, the collet must be temporarily removed from the handpiece.
The present invention is directed toward providing a dental tool handpiece assembly which will facilitate utilization of tool members of different lengths and which will provide a substitute tool abutment surface within the bore of a handpiece tool collet when a shorter tool member must be used.